Pawl and ratchet mechanism



Sept. 9, 1969 Fig.1.

J. E. HYLAN PAWL AND RATCHET MECHANISM Filed Nov. 15. 1 967 INVENTOR.

ATTORNEY.

United States Patent 3,465,605 PAWL AND RATCHET MECHANISM John E. Hylan, Birmingham, Mich., assignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Nov. 15, 1967, Ser. No. 683,187 Int. Cl. F16h 27/02 U.S. Cl. 74142 2 Claims ABSTRACT OF THE DISCLOSURE The disclosure embodies a ratchet wheel for rotating the platen to line space a record sheet and includes mechanism for positioning the ratchet wheel. The ratchet wheel is intermittently rotated by a pawl, the motion of which is a function of two cyclically and sequentially operable cams. The pawl is mounted to pivot about a first axis and to revolve about a second axis such that the wheel is stopped in the desired indexed position.

Summary of the invention The invention resides in the provision of a pivotal and revolvable pawl operating mechanism for operatively connecting cylically and sequentialy operable cams to index and position a ratchet wheel.

It is an object of the invention to provide a mechanism in which cylically and sequentially operable cams impart to a pawl a compound motion to the effect that a ratchet wheel acted upon by the pawl is not only rotated inter mittently but is also stopped by the pawl in the desired position.

It is also an object of the invention to provide a mechanism in which the pawl is slidably pivoted between the cams and the ratchet wheel to the effect that, should the ratchet wheel be prevented from rotating, the mechanism will not be damaged.

FIG. 1 is a said view of a pawl and ratchet indexing mechanism, embodying features of the invention, and

FIG. 2 is a view similar to FIG. 1 illustrating the motion of the parts in the indexing operation.

With reference to the drawings, the mechanism includes a supporting means or frame structure 10, a ratchet wheel 12, operating mechanism 14 and a motion transmitting mechanism 16. The ratchet wheel 12, operating mechanism 14 and the motion transmitting mechanism 16 may be mounted on a pair of upright side frame members 18 of structure 10, of which only one is shown. The ratchet wheel 12 and the operating mechanism 14 are spaced apart with the motion transmitting mechanism 16 therebetween.

The ratchet wheel 12 is afiixed onto a rotatable shaft 20 which may be the shaft of a printing platen 21 to be indexed through predetermined angular displacement for line spacing a record sheet (not shown). A rotatable camshaft 22 has a pair of cams 24 and 26 affixed thereon, the camshaft being journaled on the side members 18 parallel to the ratchet shaft 20. Also, the camshaft 22 is preferably a cyclically operable shaft, initiated, for example, by a cycling operation of a business machine motor through the well-known one-revolution clutch.

The cam 24 has a high surface 27 and a longer low surface 28 connected by a cam step 30 and a cam riser 32. The other cam, or cam 26, may be an eccentric having a high point 33 and a low point 34. The cams are relatively arranged for sequential operation, cam 24 being considered a first cam and cam 26 the second cam with respect to their operating sequence.

In order to effect indexing of the ratchet wheel 12 in a manner to stop the ratchet wheel in the desired position, a rockable bail 36 is pivotally mounted, as at 37, on the side member 18 and has an upwardly extending arm 38 3,465,605 Patented Sept. 9, 1969 ice on which an elongated pawl 40 is pivotally mounted, as at 42. One end of the pawl 40 overlies the ratchet wheel 12 and is provided with teeth 44 to mesh with the ratchet wheel teeth. The other end of the pawl 40 carries a cam follower 46 which is yieldingly held against the cam 24 by a spring 48. The upper end of the bail arm 38 is bifurcated, as shown, to receive the pivot pin 42; and one ofi the legs of the bifurcation is extended for attachment to a coil spring 50. It will be seen that the coil spring 50 yieldingly holds a cam follower 52, on a lower arm 53 of the bail 36, against the cam 26 and urges the bail to rock clockwise, as viewed in the drawing. The rockable bail 36 thus provides a movable or rockable fulcrum for the pawl 40, and angular displacement of the bail by cam 26 determines the stroke of the pawl. The movable or rockable fulcrum of the pawl 40 is the lower end of a slot 54 of the bifurcated upper end of bail arm 38. This connection provides for relative movement between the pawl 40 and ratchet wheel 12 if for some reason the latter is prevented from rotating.

Operation With reference to FIG. 1, assuming that the mechanism is in operation, the cam 24 rotates clockwise and the follower 46 rides down the incline 30 whereupon the spring 48 pivots the pawl 40 counterclockwise to disengage the toothed end of the pawl from the ratchet wheel 12. At this time, the follower 52 rides down the gradual incline of the cam 26 whereupon the bail 36 is pivoted clockwise by the spring 50 so that the pawl 40 revolves clockwise about the pivot pin 37 over the teeth of the ratchet wheel. By this time, the follower 46 rides up the cam riser 32 whereupon the pawl 40 is pivoted clockwise to engage its toothed end in mesh with the next tooth of the ratchet wheel 12. This is followed by the cam 26 pivoting the bail 36 counterclockwise which carries the pawl back to the position shown in FIG. 1. In the last operation, the pawl not only advances or indexes the ratchet wheel, but stops the wheel in the proper position. It will be appreciated by those skilled in the art that the mechanism may operate continuously so as to intermittently line space a record sheet, or the mechanism could be initiated manually. In the latter case, the pawl 40 would have a starting position which could either be the position shown in FIG. 1 or the position shown in FIG. 2. In this regard, I prefer to consider the position of the pawl in FIG. 2 as the starting position, although it is apparent that the starting position is not critical to the invention.

While I have shown and described the wheel indexing mechanism in considerable detail, it will be understood that many changes and variations may be made therein without departing from the spirit and scope of the invention.

I claim:

1. A mechanism for rotating 2. platen to line space a record sheet comprising supporting means, a ratchet wheel to be operatively connected to the platen and rotatably mounted on said supporting means, a first cam spaced from and rotatable about an axis parallel to the axis of said ratchet wheel, a second cam spaced from and rotatable about an axis parallel to the axis of said ratchet wheel, a first cam follower pivoted to rock on said supporting means, a second cam follower pivoted on said first cam follower to rock therewith, said first and second cam followers biased respectively against said first and second cams, said first and second cams cyclically operable together to pivot said second cam follower and then rock said first cam follower to reciprocate the latter, and rigid pawl carried by said second cam follower and normally engaging and holding said ratchet wheel against rotation.

2. A mechanism for rotating a platen to line space a record sheet as defined by claim 1 wherein said second 3 cam follower is pivoted on said first cam follower by a pin mounted on said second cam follower, said pin being slidably guided radially with respect to the rocking motion of said first cam follower in a slot in said first cam follower.

References Cited UNITED STATES PATENTS 2,868,026 1/1959 Finehout et al 74142 2,917,933 12/1959 Harris 74-575 FRED C. MATTERN, JR., Primary Examiner 5 W. S. RATLIFF, JR., Assistant Examiner US. Cl. X.R. 

